TruAirspeed is a True Airspeed Calculator for the iPhone. It's a bit different from other true airspeed calculators, in which the pressure altitude is an input. This requires resetting the altimeter to the standard sea level pressure of 29.92"Hg to read the pressure altitude. With TruAirspeed, you input the indicated altitude and the Kollsman window's pressure setting — the app then calculates the pressure altitude, density altitude and true airspeed. The calculations take compressibility effects into account, but not shock waves, so it's limited to subsonic, non-transonic flight only.

The user has a choice of units for inputs and results, and may also set a correction factor for his/her bird's airspeed indicator/pitot-static system, if known.